Magnetic sensor circuit

Abstract

Provided is a magnetic sensor circuit and includes: a magnetic sensor outputting a first sensor signal based on a magnetic flux density in a first direction; a magnetic sensor outputting a second sensor signal based on a magnetic flux density in a second direction orthogonal to the first direction; a signal processing circuit respectively obtaining a first detection signal and a second detection signal which transition between low and high levels based on the first magnetic sensor signal and the second magnetic sensor signal; a driver outputting a first output voltage based on the first detection signal; a driver outputting a second output voltage based on the second detection signal; and a voltage monitoring circuit generating mode signals whose signal levels transition based on transitions of voltage levels of the first output voltage and the second output voltage input thereto.

What is claimed is: 
     
       1. A magnetic sensor circuit, comprising:
 a first magnetic sensor which detects a magnetic flux density in a first direction and outputs a first sensor signal based on the detected magnetic flux density in the first direction; 
 a second magnetic sensor which detects a magnetic flux density in a second direction orthogonal to the first direction and outputs a second sensor signal based on the detected magnetic flux density in the second direction; 
 a signal processing circuit which contains a mode signal input port from which mode signals are received, a first sensor signal input port from which the first sensor signal is received, and a second sensor signal input port from which the second sensor signal is received, and which is configured to switch between a normal mode and a test mode in which a predetermined operation different from that of the normal mode is performed, wherein in the normal mode, a first detection signal which transitions between low and high levels is output based on the first sensor signal, while a second detection signal which transitions between low and high levels is output based on the second sensor signal; 
 a first driver from which the first detection signal is received in the normal mode while a test signal is received in the test mode, and which outputs a first output voltage based on the received first detection signal or the received test signal; 
 a second driver from which the second detection signal is received in the normal mode while the test signal is received in the test mode, and which outputs a second output voltage based on the received second detection signal or the received test signal; and 
 a voltage monitoring circuit which receives the first output voltage and the second output voltage, and generates the mode signals having a plurality of different signal levels in accordance with transition patterns of voltage levels of the received first output voltage and the received second output voltage. 
 
     
     
       2. The magnetic sensor circuit according to  claim 1 , wherein the voltage monitoring circuit includes:
 an output voltage input port from which the first output voltage and the second output voltage are received; 
 a mode signal generation circuit in which any number of two to four specific transition patterns are set from the transition patterns in which the transition of the voltage level of the first output voltage input from the output voltage input port and the transition of the voltage level of the second output voltage input from the output voltage input port occur within a predetermined time, and which generates the mode signals having the same number as a set number of the specific transition patterns and respectively having different signal levels; and 
 an output port which outputs the mode signals generated by the mode signal generation circuit. 
 
     
     
       3. The magnetic sensor circuit according to  claim 2 , wherein the mode signal generation circuit includes:
 a first edge detection circuit which detects a rising edge and a falling edge of the first output voltage, and which generates a first rising edge detection signal corresponding to the detected rising edge and a first falling edge detection signal corresponding to the detected falling edge; 
 a second edge detection circuit which detects a rising edge and a falling edge of the second output voltage, and which generates a second rising edge detection signal corresponding to the detected rising edge and a second falling edge detection signal corresponding to the detected falling edge; 
 a determination circuit which determines presence or absence of the specific transition patterns based on the first rising edge detection signal, the first falling edge detection signal, the second rising edge detection signal, and the second falling edge detection signal, and which generates a determination result signal indicating a determination result; and 
 a signal generation circuit which generates the mode signals based on the determination result signal. 
 
     
     
       4. The magnetic sensor circuit according to  claim 3 , wherein the determination circuit is configured to determine the presence or absence of the two to four specific transition patterns which are set among four patterns containing a first pattern in which both the voltage level of the first output voltage and the voltage level of the second output voltage transition from a low level to a high level within the predetermined time, a second pattern in which the voltage level of the first output voltage transitions from a low level to a high level and the voltage level of the second output voltage transitions from a high level to a low level within the predetermined time, a third pattern in which the voltage level of the first output voltage transitions from a high level to a low level and the voltage level of the second output voltage transitions from a low level to a high level within the predetermined time, and a fourth pattern in which both the voltage level of the first output voltage and the voltage level of the second output voltage transition from a high level to a low level within the predetermined time. 
     
     
       5. The magnetic sensor circuit according to  claim 1 , comprising:
 a third magnetic sensor which detects a magnetic flux density in a third direction orthogonal to the first direction and the second direction, and which outputs a third sensor signal based on the detected magnetic flux density in the third direction; and 
 a third driver from which a third detection signal is received in the normal mode while the test signal is received in the test mode, and which outputs a third output voltage based on the received third detection signal or the received test signal; 
 wherein the signal processing circuit contains a third sensor signal input port from which the third sensor signal is received, and is configured to switch between the normal mode and the test mode, wherein in the normal mode, the third detection signal based on the third sensor signals as well as the first and second detection signals are output, the third detection signal transitioning between low and high levels; and 
 the voltage monitoring circuit is configured to generate the mode signals having a plurality of different signal levels in accordance with transition patterns of voltage levels of the first output voltage, the second output voltage, and the third output voltage. 
 
     
     
       6. The magnetic sensor circuit according to  claim 5 , wherein the voltage monitoring circuit comprises:
 an output voltage input port from which the first output voltage, the second output voltage, and the third output voltage are received; 
 a mode signal generation circuit in which any number of two to eight specific transition patterns are set from transition patterns in which the transition of the voltage level of the first output voltage input from the output voltage input port, the transition of the voltage level of the second output voltage input from the output voltage input port, and the transition of the voltage level of the third output voltage input from the output voltage input port occur within a predetermined time, and which generates the mode signals having the same number as a set number of the specific transition patterns and respectively having different signal levels; and 
 an output port which outputs the generated mode signals. 
 
     
     
       7. The magnetic sensor according to  claim 6 , wherein the voltage monitoring circuit further comprises a selection circuit which selects two output voltages from the first output voltage, the second output voltage, and the third output voltage which are received from the output voltage input port; and
 the specific transition patterns are set to any number of two to four among the transition patterns of the voltage levels of the two output voltages selected by the selection circuit.